NMR logging using time-domain averaging

Inactive Publication Date: 2006-11-14
HALLIBURTON ENERGY SERVICES INC
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  • Abstract
  • Description
  • Claims
  • Application Information

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Benefits of technology

[0012]In a preferred embodiment the present invention uses time-domain average of single event data to increase the SNR, but not stacking of data from multiple events, and hence, achieves higher spatial resolution. In accordance with the present invention, the SNR can be increased also by application of both the tim

Problems solved by technology

When the logging speed is slow, the tool moves only a short distance.
However, when the logging speed is relatively fast, the tool moves over longer distances and the formation properties may change significantly over the distance.
As a result, stacking of echo train data from multiple events, as generally used in the prior art, reduces apparent spatial resolution of measuremenets beyond the intrinsic resolution of the tool.
Enhancing the resolution of the logs is a significant problem, because subsurfa

Method used

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Embodiment Construction

[0023]The method in accordance with the present invention will be described next in the context of NMR logging and will use terminology generally accepted in this field. It should be understood, however, that the method is equally applicable to processing of data from any number of other logging applications, and more generally to processing of data that can be modeled as an exponential function of time.

[0024]With reference to the NMR logging applications discussed above, in accordance with the present invention, the T2 decay time distribution can be obtained by inverting the time-domain echo train data, assuming the following physical model:

[0025]S⁡(t)=∑T2⁢⁢ϕ⁡(T2)⁢exp⁡(-t / T2)+Noise

where φ (T2) is the porosity (or population) of the pores corresponding to the exponential decay time T2. One such example of echo-train is plotted in FIG. 1, where the echo train is generated from the T2 distribution, φ (T2), which is illustrated in FIG. 2. Because of noise, the inverted T2 distribution ...

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Abstract

Method for data acquisition and processing, which uses time-domain averaging to increase the signal to noise ratio (SNR) in single-event measurements. In a preferred embodiment, NMR echo-trains obtained using high-speed NMR logging are provided, the echo trains are time-domain averaged, preferably in real-time, over one or more time intervals to sharpen the spatial resolution of the logging tool and/or to increase the signal to noise ratio (SNR) of the data train.

Description

FIELD OF THE INVENTION[0001]The present invention concerns logging applications and more specifically relates to a method for data acquisition and processing, which uses time-domain averaging to increase the signal to noise ratio (SNR) or to sharpen the spatial resolution of the obtained logging data. In an exemplary application, the method is used in nuclear magnetic resonance (NMR) logging to increase the SNR of single event echo-train for high-speed NMR logging and / or to sharpen the spatial resolution of the received data.BACKGROUND OF THE INVENTION[0002]In oil and gas exploration it is desirable to understand the structure and properties of the geological formation surrounding a borehole, in order to determine if the formation contains hydrocarbon resources (oil and / or gas), to estimate the amount and producibility of hydrocarbon contained in the formation, and to evaluate the best options for completing the well in production. A significant aid in this evaluation is the use of ...

Claims

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Application Information

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IPC IPC(8): G01V3/00G01V3/32
CPCG01V3/32
Inventor HAGIWARA, TERUHIKO
Owner HALLIBURTON ENERGY SERVICES INC
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